docs(types): chain_id on Payment, finality_tag on SyncBlockchain

README.md

@@ -243,6 +243,11 @@ client.disputes.list(status: "closed", sort: "-opened_at")
 `payments.list`/`transactions`/`disputes` and `disputes.list` return a paginated
 `{ data:, meta: { page:, per_page:, total: } }` envelope.
 
+Every payment row carries `chain_id`, list rows included. You need it to display
+an amount: `amount` is in base units and the token's decimals resolve from
+`token` **plus** its chain — an address alone identifies a token only within one
+chain — so a listing never needs a `get(id)` per row to render totals.
+
 ### Refund (two-phase EIP-3009)
 
 ```ruby

lib/rail0/types.rb

@@ -164,6 +164,8 @@ module Types
     Payment = Struct.new(
       :id,                    # String
       :contract_id,           # String
+      :chain_id,              # Integer — EVM chain id of the deployment. On list rows too: `amount` is
+      #                         base units, and the token's decimals resolve from `token` PLUS its chain.
       :rail0_id,              # String — Protocol-level identifier (66-char hex).
       :status,                # String
       :mode,                  # String
@@ -269,7 +271,9 @@ module Types
     SyncBlockchain = Struct.new(
       :chain_id,                # Integer
       :start_block,             # Integer
-      :required_confirmations,  # Integer
+      :required_confirmations,  # Integer — Fallback burial depth, used where the chain serves no finality tag.
+      :finality_tag,            # String — Which block the chain calls settled ("safe", "finalized" or
+      #                           "depth"); the indexer gates every notify on it.
       :explorer_url,            # Block explorer base URL; null when the chain has none.
       :network_type,            # String — "testnet" or "mainnet"; selects which chains a deployment indexes.
       :rpc_urls,                # Array — Ordered list of public RPC endpoints tried in turn (serial fallback).